The head is round, hardly differentiated from the remarkably long and mobile neck. The body is thick-set, short, and with great mobility of the vertebral column; the arms are slender and very long, a full third longer than the legs; the tail is short and stubby.The whole animal is covered with long coarse but soft and silky hair, which serves as a thatch in rain and with the dense under fur, as a real protection against the attack of many foes. The general colour of this species is grizzled drab, with irregular patches of dirty white on the dorsal surface. The males are highly coloured for mammals, having bright orange ear patches and a rounded spot of the same colour in the middle of the back.Very rarely an adult female sloth will have dull orange ear patches, but never the brilliant back marking (Beebe,1926).The pale-throated sloth can be distinguished from other species of sloth by its paler throat (white or yellowish buff) in combination with the pale forehead and the lack of dark facial marks (Gardner, 2007).The neck contains nine cervical vertebrae.The forelimbs are slightly longer than the hind limbs and each forefoot has three long claws.The sloth’s digits are bound together with gristle and flesh so the claws are fairly immoveable; the strong sharp claws are almost semicircular, measuring up to about 7.5 cm (Merret, 1983).
Head and body length averages 50-60 cm and tail length 5 to 6 cm.Bradypus have a body weight of 4 - 4.5 kg (Merret, 1983).
Reproduction is thought to occur throughout the year, with one young born annually, following a gestation period of 4 to 6 months (Hayssen et al., 1993). Most births occur at the beginning of the dry season from late July to September in northern Guyana (Beebe, 1926).
The three-toed sloth inhabits tropical rain forests from southern Central America to north-eastern Argentina ( http://www.ed.final.gov/linc/spring96/projects/rainforest/rainhtual1996).
Biogeographic Regions: neotropical (Native )
Three-toed sloths inhabit forests and spend practically their entire life in the trees, where they hang beneath the limbs or sit in a fork (Nowak,1999).The species is almost exclusively arboreal, but also swims well. The sloth is capable of moving distances of several miles, travel that may require moving over ground and swimming across rivers (Gardner, 2007).
This species occurs in the Guyana Shield region, from Venezuela south of the Orinoco (although its distribution crosses at the delta region) into northern Brazil (south to the Amazonas/Solimões), through to Guyana, Suriname and French Guiana. The species has also been found in eastern Colombia by the department of Caquetá (IUCN).
Bradypus tridactylus is a strange animal. It has almost no tail or external ears, and its head is slightly rounded with a blunt nose. The body is covered with long and course hair. Very small green algae sometimes live mutualistically in the pits of the hair, which gives the sloth an overall greenish appearance that camouflouges it in the forest canopy. Male sloths have a bright yellow or orange patch on the back. The females have two mammae in the chest region. The three-toed sloth is armed with long, compressed, arched, hollowed claws, of which the middle claw is the largest. Bradypus tridactylus grows to a length of between 1.5 and 2.5 ft. The limbs are long and weak, with anterior extremities that are nearly double the length of the posterior. The three-toed sloth has 9 neck vertebrate, which grant it extreme flexibility (Cuvier).
Range mass: 2.25 to 5.5 kg.
Habitat and Ecology
The three-toed sloth lives high in the canopy of tropical rainforests (www.hillside.sowashco/95-96/palmquist/rainforest/rainhtual).
Terrestrial Biomes: rainforest
The three-toed sloth is herbivorous. It feeds exclusively on twigs, buds, and leaves of trees of the genus Cecropia. Because of its limited diet, the species does not do well in captivity ( http://www.geocites.com/Hollwood/set/1478/Sloth.html , 1996).
Life History and Behavior
Sloths sleep or rest for about 20 hours a day (Beebe, 1926). The three-toed sloth is mainly active during the day but can be active at night (Sunquist and Montgomery, 1973)Sloths are beautifully adapted to arboreal life. Their movements are slow and deliberate as they select the boughs to cling to with great care and safety. The species is almost exclusively arboreal, but does move over ground and also swims well. The sloth is capable of moving distances of several miles, travel that may require moving across ground and swimming rivers (Gardner, 2007).It is a mistaken idea that sloths spend all of their lives upside-down. When travelling and feeding, they do hang suspended, but quite as often they are climbing or clinging on vertical stems, or actually sitting down, as when asleep (Beebe, 1926).
With the exception of mother-young pairs, Bradypus tridactylus are usually solitary and exhibit aggressive behaviour when confined together in captivity (Gardner, 2007).
Lifespan, longevity, and ageing
Bradypus tridactylus mates high in the safety of the trees. After birth the males do not display any parental care. It gives birth to a single, very small young, usually in the beginning of the dry season, March - April. Gestation typically lasts 5-6 months. After birth, the offspring enjoys belly-to-belly nurturing for six months. At four months, it can begin to feed on foliage, having first sampled it at two weeks of age from its mother's lips. Sloths inherit not only their mother's preference for particular kinds of leaves but also the specialized gut flora to digest them. When a young sloth has mastered the rudiments of arboreal life, its mother simply departs, leaving it to its life in the tropical canopy (World Book,1996; www.press.jhu.edu/books/walker/).
Average gestation period: 141 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 1095 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1642 days.
Evolution and Systematics
Molecular Biology and Genetics
Barcode data: Bradypus tridactylus
There is 1 barcode sequence available from BOLD and GenBank. Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen. Other sequences that do not yet meet barcode criteria may also be available.
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Download FASTA File
Statistics of barcoding coverage: Bradypus tridactylus
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2006Least Concern(IUCN 2006)
- 2006Least Concern
Bradypus tridactylus has become so highly specialized for arboreal life that it is severly handicapped if removed from the forest canopy. Also, this mammal does not survive in captivity very well. With the rapid decimation of the rain forests, due to the activities of lumber companies and a growing number of farmers and miners, these mammals will certainly be affected (www. geocites.com/Hollwood/set/1478/Sloth.html).
IUCN Red List of Threatened Species: least concern
The IUCN lists this species as ‘Least Concern’ in view of its wide distribution in one of the most pristine areas of the Amazon basin, and its having been recorded as relatively locally abundant .(IUCN, 2009).Bradypus tridactylus are widespread and locally abundant within a spectrum of protected areas, from inner city parks to wilderness reserves (Vizcaino & Loughry, 2008).
All species of Bradypus may be threatened by habitat destruction and excessive hunting (Nowak, 1999).The main predators are the
- harpy eagle
- margay cat
Relevance to Humans and Ecosystems
Economic Importance for Humans: Positive
The three-toed sloth in its remote habitat rarely has the chance to affect a human life. It is food to jaguars and ocelots, from which skins are used for human enjoyment. (www.geocites.com/Hollwood/set/1478/Sloth.html).
The pale-throated sloth (Bradypus tridactylus) is a species of three-toed sloth that inhabits tropical rainforests in northern South America. It is similar in appearance to, and often confused with, the brown-throated sloth, which has a much wider distribution. Genetic evidence has been interpreted to suggest the two species diverged only around 400,000 years ago, although the most recent evidence indicates the split was closer to 6 million years.
Pale-throated sloths have a rounded head with a blunt nose and small external ears. The limbs are long and weak, with the arms being nearly twice the length of the hindlimbs. The hands and feet each have three digits, armed with long, arched claws, with the middle claw being the largest and most powerful. Males are 45 to 55 centimetres (18 to 22 in) in head-body length, with a short, 4 to 6 centimetres (1.6 to 2.4 in), tail, and weigh from 3.2 to 6 kilograms (7.1 to 13.2 lb). However, the females are noticeably larger, being from 50 to 75 centimetres (20 to 30 in) in length, and weighing 3.8 to 6.5 kilograms (8.4 to 14.3 lb).
The body is covered with coarse guard hairs up to 10 centimetres (3.9 in) long, with a finer undercoat. Green algae live mutualistically between the microscopic scales on the surface of the guard hairs, giving the sloth a somewhat greenish appearance that serves as camouflage. Adults are blackish-grey over most of the body, with darker patches distributed over the backs, shoulders, and hips. Males have a bright yellow or orange patch on the back, divided by a central black stripe. Pale-throated sloths are difficult to distinguish from the closely related brown-throated sloth, but, as their name implies, have a pale yellow patch on the throat.
The eyes are large and forward facing for binocular vision, with round pupils. Unusually, they appear to lack any cone cells in the retina, suggesting that the sloth is unable to see color. Despite its apparently small ears, the pale-throated sloth has excellent hearing; it has also been reported to have a good sense of smell.
The sloth has nine cervical vertebrae, giving it extreme flexibility. As a result, a pale-throated sloth can bend its head backwards and forwards through 270° and rotate it through 330°. It possesses a pair of foramina in the anterodorsal nasopharynx, a feature that distinguishes it from its sister species. The females have two mammae in the chest region, a simple uterus. Males have no discrete prostate gland, no scrotum, and only rudimentary seminal vesicles.
The mouth is lined by a black colored mucosa, although the large and heavy tongue is pink. The palate is wrinkled in texture, and the tongue is lined with numerous grooves, apparently adaptations to the sloth's diet. Like other three-toed sloths, it has just five teeth on each side of the upper jaw, and four on each side of the lower jaw; these are all simple and rounded in shape, with the front teeth in the upper jaw being much smaller than the others. The esophagus is short, but the stomach is large and complex, and there is also a large diverticulum in the cecum. 
Distribution and habitat
The pale-throated sloth is found only in the tropical forests of northern South America, including Guyana, Suriname, French Guiana, western Venezuela and Colombia, and Brazil north of the Amazon River. There are no recognised subspecies.
Behavior and biology
Pale-throated sloths are solitary, herbivorous animals that spend almost their entire lives in trees. Depending on habitat, population densities of anything from 1.7 to 221 per square kilometre (4.4 to 572.4 /sq mi) have been reported. They eat only leaves, including those of Cecropia, Ceiba, Elizabetha, and Hevea. Known predators include jaguars, margays, harpy eagles, and anacondas.
The pale-throated sloth can hang so securely with its hooklike claws that it even falls asleep in this position. It may even stay suspended in the trees for some time after it dies. They have been reported to spend over eighteen hours each day asleep, and move through the tree canopy only very slowly. They periodically descend from the trees to defecate, depositing a pile of small pellets in a hole dug into the ground. Despite their arboreal lifestyle, they are effective swimmers. Their call is a bird-like whistle described as an "ai-ai" sound.
In addition to their mutualism with green algae, pale-throated sloths are also commensal with sloth moths, and with certain species of beetle. These insects live in the sloth's fur, and lay their eggs in its dung, on which their larvae feed.
The young are born already fully furred, and with open eyes. The young animal clings to the mother's underside for the first month of life, by which time it has reached a weight of around 300 grams (10 oz). They begin to take solid food at three weeks, and are fully weaned some time after the first month. The young initially have soft greyish-brown fur, which darkens and becomes rougher as they age. They reach sexual maturity at around three years.
- Gardner, A. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 100. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Chiarello, A. & Moraes-Barros, N. (2011). "Bradypus tridactylus". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 18 January 2012.
- Linnæus, Carl (1758). Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I (in Latin) (10 ed.). Holmiæ: Laurentius Salvius. p. 34. Retrieved 23 November 2012.
- Barros, M.C. et al. (2003). "Phylogenetic analysis of 16S mitochondrial DNA data in sloths and anteaters". Genetics and Molecular Biology 26 (1): 5–11. doi:10.1590/S1415-47572003000100002.
- Moraes-Barros, M.C. et al. (2011). "Morphology, molecular phylogeny, and taxonomic inconsistencies in the study of Bradypus sloths (Pilosa: Bradypodidae)". Journal of Mammalogy 92 (1): 86–100. doi:10.1644/10-MAMM-A-086.1.
- Hayssen, V. (2009). "Bradypus tridactylus (Pilosa: Bradypodidae)". Mammalian Species 839: 1–9. doi:10.1644/839.1.
- Taube, E. et al. (1999). "Distribution of two sympatric species of sloths (Choloepus didactylus and Bradypus tridactylus) along the Sinnamary River, French Guiana". Biotropica 31 (4): 686–691. doi:10.1111/j.1744-7429.1999.tb00418.x.
- Taube, E., et al. (2001). "Reproductive biology and postnatal development in sloths, Bradypus and Choloepus: review with original data from the field (French Guiana) and from captivity". Mammalian Species 31 (3-4): 173–188. doi:10.1111/j.1365-2907.2001.00085.x.
- BBC Science and Nature. "Wildfacts - Pale throated Three-toed Sloth". Retrieved 2007-01-02.